Fluidic irrigation

ABSTRACT

Fluidic techniques and elements are disclosed for performing various irrigation functions, including sequential filling of irrigation ditches by automatic operation of fluidic diverter elements. A novel diverter element is disclosed which is operable either as a switching or proportional type fluidic amplifier, and includes a weir formed at the downstream end of its output passages and a vortex chamber projecting outwardly from its interaction region for converting part of the power stream flow to vortical flow which augments aspiration of ambient control fluid. In a further aspect of the invention, hard cut-off of liquid flow is achieved with a roller curtain gate comprising a flexible sheet adapted to be selectively rolled or unrolled over a flow opening. Also disclosed is a fluidic control for a siphon whereby venturi action in a fluidic element is employed to create a suction force which initiates siphon flow. A number of fluidic level sensing schemes are disclosed for controlling sequential irrigation ditch filling, and fluidic techniques are disclosed which compensate for environmental factors in the level detection schemes.

United States Patent Freeman July 1 l, 1972 54] FLUIDIC IRRIGATION Primary Examiner$amuel Scott [72] Inventor: Peter A. Freeman. Baltimore, Md. and

[73] Assignee: llowles Fluldlcs Corporation {5 7] ABSTRACT [22] Filed: July 17, 1969 Fluidic techniques and elements are disclosed for performing Appl. No.: 842,599

[52] [5|] lnt.Cl. ..Fl5c l/04,Fl5c M6 [58] FieldolSeu-ch ..l37/8l.5;235/20l;239/2l2, 239/213 [56] References Cited UNITED STATES PATENTS 3,331,380 7/1967 Schonfeld et al. ..l37/8 L5 3,148,691 9/1964 Greenblott I 37/8 1 .5 3,l58,l66 ll/l964 Warren ..l37/8l.5 3,2l6,439 ll/l965 Manion ....l37/8 L5 3,267,946 8/1966 Adams et al. 1 37/8l.5 3,267,949 8/1966 Adams ....l37/8l.5 3,277,914 l0/l966 Manion l37/8|.5 3.476,|3l ll/l969 Darison et al ..l37/8l.$

various irrigation functions. including sequential filling of irrigation ditches by automatic operation of fluidic diverter elements. A novel diverter element is disclosed which is operable either as a switching or proportional type fluidic amplifier. and includes a weir formed at the downstream end of its output passages and a vortex chamber projecting outwardly from its interaction region for converting part of the power stream flow to vertical flow which augments aspiration of ambient control fluid. In a further aspect of the invention. hard cutoff of liquid flow is achieved with a roller curtain gate comprising a flexible sheet adapted to be selectively rolled or unrolled over a flow opening. Also disclosed is a fluidic control for a siphon whereby venturi action in a fluidic element is employed to create a suction force which initiates siphon flow A number of fluidic level sensing schemes are disclosed for controlling sequential irrigation ditch filling, and t'luidic techniques are disclosed which compensate for environmental factors in the level detection schemes.

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FLUIDIC IRRIGATION BACKGROUND OF THE INVENTION The present invention relates to fluidics technology, and in particular to fluidic techniques utilized in controlling irrigation systems.

The need for automation in irrigation is becoming acute in many of the nation's large agriculture areas where natural rain fall must be greatly augmented with irrigation water. The need arises primarily from the increasing costs and shortage of manual labor which has been traditionally used to operate irrigation systems. In limited areas, this problem is being attacked by the automation of sprinkler irrigation systems; however, these require the combination of available electricity at a high power level to operate pumping facilities. The pumps and associated plumbing of sprinkler systems also represent a large capital investment, which is currently economically unfeasible in most of the irrigated farm areas. The automation of surface irrigation systems therefore is currently lacking badly for want of a practical low cost technical approach. The automatic irrigation techniques, primarily fluidic techniques, described herein have been well received in the industry and represent a very promising approach to the solution of an eminently serious agricultural problem.

it is therefore a primary object of the present invention to provide techniques for use in automating irrigation control systems.

it is another object of the present invention to employ fluidic techniques for providing relatively inexpensive automatic control capabilities in irrigation control systems.

The overall system concept described herein employs fluidic diverter elements operable in various sequences and combinations of sequences to distribute water as required among a plurality of irrigation ditches. In implementing the system it was necesSary to develop novel fluidic diverter elements, novel liquid level detection and control techniques, novel flow shut-off devices, and novel techniques for adapting the irrigation system to changes in the localized environment. These various elements and techniques, as well as the overall system concept, all form a part of the present invention. For example, assume that eight irrigation ditches are to be filled in sequence so that when one ditch fills up flow is to be switched to the second, etc. This can be accomplished automatically by using a series of bistable fluidic diverters and associated liquid level sensors arranged to sequentially switch the diverters accordingly as each ditch is filled. It was found that conventional fluidic bistable elements were not able to divert large mass flows of water nor were they able to respond accurately to conventional liquid level detection and flow control techniques. Consequently novel diverter elements and associated level detection and flow control techniques were conceptualized for particular utilization in irrigation control systems, although these elements and techniques have a somewhat broader application apart from irrigation systems.

It is therefore another object of the present invention to provide a novel fluidic diverter element for particular utilization in irrigation control systems.

It is another object of the present invention to provide novel flow control techniques for facilitating the regulation and shut-off of large mass liquid flows, as required in irrigation systems.

it is still another object of the present invention to provide liquid level detection and control techniques having particular utilization in irrigation control systems.

SUMMARY OF THE PRESENT INVENTION In accordance with one aspect of the present invention a novel fluidic diverter element of the wall attachment type selectively diverts large mass flows of water at relatively low dynamic pressures. The diverter has relatively wide outlet passages as compared to those of conventional fluidic diverter devices, and has weir structures formed at the downstream ends of its outlet passages. The weirs prevent water in the nonflowing outlet passage from spilling over into the irrigation ditch fed by that output passage. The switching control in the element is accomplished by controlled aspiration of ambient air through a control port. Aspiration is augmented by a vortex chamber arranged to peel off a portion of the power stream, creating vortical flow therefrom which produces a relatively large suction force at the control port. The augmented suction permits utilization of long lengths of control lines without intolerable control signal losses.

The above described diverter element can be designed for analog or proportional operation by enlarging the control port cross-section to permit sufficiently high rates of induction of ambient air to prevent attachment of the water power stream to the diverter sidewalls. The control ports may comprise fittings of different sizes so that a single diverter element can be used for either switching or proportional operation by proper choice of fittings.

The diverter control ports may communicate with liquid level detection devices which can be either bistable or analog as required. in accordance with one aspect of the present invention, a novel analog liquid level sensor employs an inverter cup having a slotted sidewall through which fluid is aspirated by a diverter control port. As the level of the liquid rises in the inverted cup, the slotted cup presents a gradually increasing flow restriction for aspirated ambient air flow to the control port. The resulting decrease in aspirated air flow produces concomitant changes in the diverter power stream position, and if the diverter is of the proportional type the diverter output pressure comprises a measure of the liquid level being sensed.

in order to provide hard cut-off of liquid flow in an irrigation system, the present invention provides a novel roller curtain gate and associated control apparatus. The gate comprises a flexible sheet of sufficient size to block liquid outflow through an aperture in a reservoir wall when the sheet is placed over that aperture. The flexible sheet has one edge secured to the wall adjacent the aperture and is adapted to be rolled and unrolled over the aperture in response to predetermined system conditions, such as level detection, turn on, etc.

A novel control arrangement for the roller curtain comprises a leaky bucket, pivotable under the weight of water to roll the curtain. The leaky bucket is fed by an outlet leg of a diverter and empties through drain holes when the diverter switches away from the bucket. The diverter is controlled, for example, by a liquid level detector so that reservoir outflow is provided as needed.

In accordance with a further aspect of the present invention, a fluidic control device is provided to initiate and terminate flow through a siphon. Siphons are presently in widespread use to transfer water from supply ditches to growing areas in irrigation systems. The present invention utilizes venturi suction from an outlet passage of a fluidic diverter element. When flow in the diverter element is through that outlet passage, venturi action sucks air from the top of the siphon neck, initiating water flow through the siphon. When flow in the diverter is switched to the other outlet passage, ambient air enters the siphon via the venturi section to cut-off siphon flow. The siphon may be rotated to provide different heights of the siphon neck.

Where hard or total shut-off capability is not required, a continuous flow type liquid level control may be employed. This comprises a vortex element controlled by a diverter element which in turn is controlled in accordance with the level of liquid. One leg of the diverter supplies flow tangentially to the vortex element to controllably induce vortical flow therein. The flow through the vortex element is radial in the absence of tangential diverter flow, the radial flow experiencing minimum impedance and hence providing maximum outflow. increased tangential flow from the diverter induces commensurate vorticity in the flow through the vortex element, and the greater the vorticity the smaller the outflow.

A number of modified liquid level detection techniques are disclosed. In one such technique an inverted cup type level detector is placed near the upstream end of an irrigation ditch and provides, an indication of the liquid level at the downstream end. This is accomplished by using the inverter cup to sense the level in a container into which liquid ingress is restricted so that the liquid level in the container rises slowly, in close approximation to the liquid level rise at the downstream end of the ditch.

Another disclosed liquid level detector is employed in an irrigation ditch and controls the frequency of filling the ditch with water. This is accomplished by employing an inverter cup in conjunction with a basin and permitting the basin to fill with liquid to a predetermined level above the level-sensing mouth of the cup shutting off the ditch supply. The evaporation rate of liquid in the basin controls the time required for the basin liquid level to fall below the cup sensing mouth and re-initiate inflow of liquid to the ditch.

A rainfall override may be provided with a liquid level detector to prevent unnecessary filling of irrigation ditches where rainfall has supplemented irrigation requirements. The rainfall override comprises a rain-collecting funnel arrangement disposed to add rain water to the basin associated with a liquid level sensing inverted cup. The amount of rain water so added is calibrated in accordance with the amount of rainfall, and filling of the ditch is delayed accordingly.

Other override devices, responsive to soil moisture content, ambient temperature, and ambient wind are disclosed in interlocking relationship with a fluidic diverter for preventing or initiating irrigation flow in accordance with these ambient conditions.

These and other fluidic elements and circuits are employed in irrigation systems which are automatically controlled as required to service one or more individual parcels of land.

BRIEF DESCRIPTION OF THE DRAWINGS The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of the various specific embodiments thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIG. I is a view in perspective of a bistable diverter valve employed in the irrigation control systems of the present invention;

FIG. la is a side view of the diverter of FIG. I;

FIG. 2 is a view in perspective of a proportional type of fluidic diverter valve employed in the irrigation control systems of the present invention;

FIG. 3 is a front view in perspective of a roller curtain gate and control apparatus capable of cutting-off liquid flow in an irrigation system;

FIG. 4 is a rear view in perspective of the roller curtain gate of FIG. 3;

FIG. 5 is a view in section illustrating the mounting of the roller curtain gate of FIGS. 3 and 4;

FIG. 6 is a diagrammatic illustration of a roller curtain control apparatus of the type illustrated in FIGS. 3 and 4 employed as an upstream liquid level control device;

FIG. 7 is a diagrammatic illustration of a roller curtain control apparatus of the type illustrated in FIGS. 3 and 4 employed as a downstream liquid level control device;

FIG. 8 is a diagrammatic illustration of a continuous flow type liquid level control arrangement suitable for use in the irrigation systems of the present invention;

FIG. 9 is a view in perspective of a fluidically controlled siphon constructed in accordance with the principles of the present invention;

FIG. 10 is a view in perspective of a modification of the embodiment of FIG. 9 wherein the siphon is adjustable in FIG. I] is a view in perspective of another embodiment of the fluidically controlled siphon of the present invention;

FIG. I2 is a diagrammatic illustration of a fluidic analog liquid level control apparatus;

FIGS. 13, I4 and 15 are diagrammatic illustrations of respective liquid level sensor devices constructed in accordance with the principles of the present invention;

FIG. 16 is a diagrammatic illustration of a liquid level sensor incorporating a rainfall override arrangement;

FIG. 17 is a schematic illustration of a two-stage fluidic diverter for irrigation applications and employing a novel fluidic interstage switching arrangement;

FIG. 18 is a diagrammatic illustration of a bistable fluidic diverter element for use in an irrigation system wherein the quantity of diverted liquid determines the switching time of the diverter element;

FIG. I9 is a schematic illustration of a fluidic irrigation diverter used in conjunction with a soil moisture detector for controlling diverter operation;

FIG. 20 is a schematic illustration of a fluidic irrigation diverter employed in conjunction with a temperature sensing element for controlling diverter operation;

FIGS. 21 and 22 are respective diagrammatic illustrations of respective wind monitoring devices for utilization in controlling irrigation diverter operation;

FIG. 23 is a schematic illustration of a fluidic flow balancing system for use in an irrigation control system;

FIG. 24 is a schematic illustration of a multiple flow balancing system employing the principals of the embodiment illustrated in FIG. 23;

FIGS. 25 and 26 are schematic illustrations of respective fluidic diverter circuits employed in an irrigation system in which diverter switching is delayed for a predetermined period of time after a detected liquid level reaches a predeter mined level;

FIG. 27 is a schematic illustration of a fluidic automatic irrigation system for use in a high sloping terrain environment;

FIG. 28 is a schematic illustration of a self-cycling multipleditch irrigation network;

FIG. 29 is a diagrammatic illustration of an irrigation scheme in which a plurality of fluidic diverters are serially arranged; and

FIGS. 30 and 3| are respective diagrammatic and schematic illustrations of a fluidic irrigation system in a relatively low slope terrain wherein fluidically controlled siphons are employed to conduct liquid from supply ditches to the area to be irrigated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and la of the accompanying drawings, there is illustrated a bistable fluidic diverter element I0 specifically arranged to divert water or liquid flow having a relatively low pressure head. Diverter element I0 may be constructed of any suitable plastic or metal material which is molded or otherwise formed to provide the various passages and channels described below. It is contemplated, though certainly not mandantory, that the element be formed by joining a top plate 11 to the edges of upstanding sidewalls l3 and I5 of a bottom plate, the plates being joined in fluid-tight relationship. A generally rectangular inlet opening 17 is adapted to receive pressurized liquid and conduct same to a narrow throat or power nozzle 19 having a downstream end which opens into an interaction region or chamber 20. The flow restriction provided by power nozzle 19 is achieved by the convergence of sidewalls I3 and 15 in a downstream direction from inlet I7. In interaction chamber 20, immediately downstream of power nozzle 19, the sidewalls I3 and 15 are provided with opposed and generally semicircular configured projections 21 and 23 extending outwardly of element It]. Control ports 25 and 27 communicate through top plate I] with respective projections 21 and 23. For the particular configuration illustrated in FIG. I, it is to be noted that control port 25 is of significantly larger cross section than control port at 27. The effect of this is described in detail below.

Immediately downstream of projections 21 and 23 respective sidewalls 13 and 15 diverge in a downstream direction at a sufficiently gradual angle to permit a water power stream to attach to either sidewall when the pressure between the power stream and the sidewall falls somewhat below ambient. This wall attachment phenomenon is well known in the fluidics art and is sometimes referred to as Coanda effect. A flow divider 29 is interposed between sidewalls 13 and 15, somewhat downstream of the projections 21 and 23, forming respective outlet passages 31 and 33. At the downstream ends of outlet passages 31 and 33 the bottom plate of diverter element It] slopes upwardly toward top plate 11 to form respective weirs 35 and 37. The important characteristic of weirs 35 and 37 is that when diverter element is placed flat on its bottom plate the uppermost portion of weirs 35 and 37 extend to the height of or slightly above the edge of top plate 11 which defines inlet opening 17. Consequently, when water flows from outlet passage 33, weir 35 prevents water in outlet passage 31 from spilling out of element 10. In effect then the weirs 35 and 37 prevent outflow of water from their respective outlet passages in the absence of a predetermined pressure or head in that outlet passage. The height of the weirs is best illustrated in FIG. la.

In operation, water entering the inlet opening 17 is diverted into either of the two outlet passages 31 and 33 and exits over a respective one of weirs 35 and 37. The fundamental operating principle of element 10 is based on wall attachment, otherwise known as the Coanda effect, where a submerged stream of fluid tends to attach itself to a closely proximate wall, in this case either of sidewalls l3 and 15. Depending upon which side of the power stream experiences a more negative pressure, the power stream attaches to that sidewall and flows out through the appropriate outlet passage. The projections 21 and 23 are arranged to scoop off a portion of the liquid stream flowing thereby, the scooped off portion creating a vortical flow pattern in the semi-circular projection. The center of the vortex creates a negative pressure which provides a suction at respective control ports 25 and 27. The suction aspirates ambient air into the divener element 10. When both control ports are wide open, pressure in the region of right control portion 27 is more negative than at left control port 25 because of the smaller cross section of right control port 27. More specifically, if both control ports are opened to ambient, less ambient air can flow in through control portion 27 than through control port 25 and therefore the pressure at the right side wall in the vicinity of projection 23 is significantly more negative than the pressure along sidewall 13 in the vicinity of projection 21. The water power stream therefore attaches to sidewall 15 and flows out through passage 33. If left control port 45 is covered or capped ambient air can no longer be aspirated into projection 21, rendering the pressure therein more negative than the pressure in projection 23. The power stream therefore switches, attaching to sidewall 13 and flowing through outlet passage 31 and over the weir 35.

For the most usual irrigation applications of element I0, tubing will be connected to control port 25, and the other end of the tubing will be connected to a liquid level detector in some liquid container or irrigation ditch. When the level in the container or ditch blocks inflow of ambient air through the tubing to control port 25, the power stream switches to outlet passage 31. When inflow through the tubing is not blocked by the liquid level being detected, the power stream flows out through outlet passage 33.

The vortex action associated with projections 21 and 23 permits stronger aspiration of ambient air than is possible in prior art fluidic diverter elements of the aspiration-control type. For example in the liquid level detectors employed in U.S. Pat. No. 3,267,949 the aspiration of ambient air is achieved solely through venturi action resulting at the power nozzle. The aspiration thus produced is satisfactory where the diverter element can be placed relatively close to the liquid level detector. However, for purposes of irrigation systems, the location at which the level is being detected may be on the order of a hundred or more feet from the location of the diverter element. In most instances, this renders the simple power nozzle venturi action too weak to achieve a position switching action in the diverter element. Consequently the increased aspiration produced by the vortex action in projections 21, 23 is required. Another novel feature of diverter element 10 of FIGS. 1 and la is the relatively wide and flat outlet passage configuration which permits issuance of a thin ribbon of water over respective weirs 35 and 37. The need for this configuration relates to the relatively low pressure of the water supplied at inlet opening 17, it being relatively difficult to obtain positive switching of a low pressure head water stream. In a typical embodiment, for a power nozzle width W, the flow divider 29 is located a distance between 4W and 6W downstream of power nozzle 19, the transverse width of each outlet passage 31 and 33 adjacent the apex of divider 29 is ap proximately 3W, and the width of each of outlet passages 31 and 33 at their downstream ends in approximately 4W. I have found that where the outlet passages are configured substantially narrower than indicated by the aforementioned exam ple, the diverter may become unstable and switch irrespective of variations in the control port flow impedance, or incomplete diversion of the water stream will result. The relatively wide outlet passage permits a better power stream diffusion action and lowers the output flow impedance; in addition the relatively large set back of the downstream portions of sidewalls 13 and 15 permits a greater memory capability for diverter element 10.

It is to be pointed out that aspiration type control of a fluidic diverter element is particularly suited to irrigation systems since the control energy is derived solely from the power stream flow, and therefore auxiliary pressure sources are not required for control purposes.

Referring now to FIG. 2 of the accompanying drawings there is illustrated a fiuidic diverter element 10' constructed in a manner similar to diverter 10 of FIG, 1 but configured slightly differently to permit analog or proportional type operation as opposed to the digital or switching operation of diverter 10. Like components in FIGS. 1 and 2 are designated by similar reference numerals, the elements in FIG. 2 being designated with primes. Like diverter 10, diverter 10' has sidewalls 13' and 15' arranged to permit attachment thereto of the power stream. The sole difference in configuration for diverter elements 10 and 10' resides in the greater control port cross section in analog diverter 10'. More specifically, control ports 25' and 27' are of substantially larger cross section than either of control ports 25 and 27. As a consequence, the mass flow rate of ambient air aspirated into diverter element 10 via control ports 25 and 27' is substantially larger than the mass low rate of ambient air aspirated into diverter element 10. Control ports 25' and 27' are made sufficiently large that when both control ports are open excess ambient air flow is aspirated to each sidewall in the proximity of projections 21 and 23'. This greatly weakens the negative pressure characteristic on both sides of the water power stream, with the result that there is little tendency for the power stream to attach to either of the sidewalls. Consequently, if, as assumed here, control ports 25' and 27' have the same cross section, the power stream divides evenly between outlet passages 31 and 33'. If the ambient air inflow through either of control ports 25' and 27' is partially attenuated, as by partial blocking of the control port, the vortical flow in the corresponding projection (21' or 23') regains some of its strength and provides an increasing negative pressure, with the result that the power stream is drawn toward the outlet passage (31' or 33) on the same side of diverter 10 as the attenuated control inflow. The degree of diversion of the power stream is proportional to the difference between control inflow rates at ports 25 and 27'. It is significant that in this approach to analog or proportional type flow diversion an interesting advantage accrues in that both analog and bistable modes operation can be obtained with the same basic element configuration; the operational mode is determined by the size of the control ports. If, as illustrated in FIGS. 1 and 2, properly sized removable inserts 26 and 28 (or 26' and 28' in FIG. 2) are provided for respective control ports 25 and 27 (or 25' and 27' the analog and bistable operational modes may be selectively chosen by merely employing the appropriate inserts. Thus, diverter element having control ports 25' and 27' of relatively large and equal cross sections, can be fitted either with inserts 26' and 28' of relatively large and equal cross sectional openings to permit analog operation; or may be fitted with inserts 26 and 28 of relatively small and unequal (or equal if no bias is desired) cross sectional openings to permit bistable operation. The inserts may threadedly or otherwise, engage their respective projections 21, 21, 23,23.

Referring now to FIGS. 3, 4 and 5 of the accompanying drawings there is illustrated a fluidically controlled water gate in accordance with the present invention. The unit comprises a roller curtain gate 40 driven by a fluidically controlled leaky bucket actuator 4]. Roller curtain 40 is intended to control outflow of a liquid, such as water, contained in a tank 43 having an aperture 45 defined through one of its sidewalls 47. The outside surface of sidewall 47 and attachments thereto are illustrated in FIG. 3 and the inside surface of sidewall 47 and attachments thereto are illustrated in FIGS. 4 and 5. Outflow through aperture 45 may be dumped directly into an irrigation ditch or, as illustrated in H0. 3, be conducted directly into the inlet opening of a fluidic diverter valve 49 such as the diverter valve illustrated in FIGS. 1 or 2. The roller curtain 40 is constructed of a flexible sheet material of such size and shape to completely cover aperture 45 when the sheet is placed flat over the aperture. A series of closely spaced parallel stiffener elements 5] are secured to the flexible sheet material and extend over a least that portion of the curtain 40 which overlies aperture 45 when the gate is closed. The stiffener elements 5] are wires or rods of metal or plastic of sufficient strength to prevent collapse of curtain 40 when subjected to fluid pressures normally experienced in tank 43 in the vicinity of aperture 45.

The top edge of curtain 40 is secured to the inside surface of sidewall 47 above aperture 45 by any suitable means such as screws 53. The entire bottom edge of curtain 40 is secured to a cylindrical roller 55. A pair of ropes or cords 57 and 59 are secured to the inside surface of sidewall 47 near the top of and behind curtain 40, for example by means of screws 53. Cords 57 and 59 and extend downwardly behind curtain 40, under roller 55 and then upwardly to respective tracks or grooves in a pair of roller elements 61 and 63 located atop sidewall 47. From roller elements 61 and 63, the cords 57, 59 extend downwardly in front of the outside surface of sidewall 47 toward the leaky bucket 41 to which the cords are secured.

The leaky bucket 41 has holes 65 in its bottom and is pivotally mounted about pivot points 67 and 69 to the outer surface of sidewall 47 somewhat above aperture 45. The bucket is pivotable between two extreme positions, in one of which the bucket extends horizontally from wall 47 in rightside-up orientation. In the other extreme position the bucket is rotated downwardly from its horizontal position. Cords 57 and 59 are secured to the bucket at a location substantially displaced from pivot points 67 and 69. It may thus be seen that the cords 57 and 59 support the roller curtain 40 and leaky bucket 41 on opposite sides of wall 47 and that the curtain is actuable in a manner similar to that in which a conventional porch screen is actuated; more specifically when bucket 41 pivots downward a force is exerted on cords 57 and 59 in front of wall 47, which acts to roll the roller curtain 40 upward to permit outflow of water from container 43 via aperture 45. When the bucket pivots upwardly toward its horizontal position cords 57 and 59 become slack and roiler curtain 40 is permitted to unroll and block outflow via aperture 45.

The water pressure inside container 43 seals the roller curtain 40, along its edges, against the inner surface of sidewall 47, assuring that there is no leakage of water from the tank through aperture 45. The forces required to roll the curtain are relatively small as compared with the force required to pull a cover or valve in a sliding relationship across an aperture such as 45 in a tank. In fact, the primary forces required, except for the elastic restraint in rolling up the curtain, are principally the Bernoulli forces which occur when the roller curtain nearly closes aperture 45.

In the absence of at least a predetermined weight of water or other liquid in bucket 41 the bucket remains substantially horizontal, corresponding to the closed position of the roller curtain gate 40. When the weight of water in the bucket ex ceeds the predetermined weight, the bucket pivots, and as described above, causes the roller curtain gate to open permitting outflow via aperture 45. Thus, by controlling the amount of water in bucket 41, control of roller curtain gate 40 is achieved. Control over water in the bucket is achieved as follows: A fluidic diverter element 7], for example of the types described in relation to FIGS. 1 and 2 or a more conventional type, is mounted to the outside surface of wall 47 at aperture 45 so as to receive water outflow from container 43 at its power nozzle 72. The water thus received is converted to a power stream of water which can be controllably diverted to either of two outlet passages 73 and 75 by controlling aspiration of ambient air through control ports 77 and 79. When the power stream is diverted to outlet passage 73 it is dumped into the leaky bucket 4!, and when it is diverted to outlet passage 75 it is dumped somewhere other than leaky bucket 41, for example to an irrigation ditch fed by diverter 49.

The leaky bucket 41 thus utilizes the weight of water therein to provide an actuating force to raise the roller curtain 40. Bucket 41 is selectively filled by the small diverter valve 71 when the diverter is switched to issue water through outlet passage 73. The water empties slowly through holes 65. Diverter 71 is sized so that its outflow from passage 73 is roughly twice the leakage flow through drain holes 65. The bucket 4] is thus actuated to its extreme downward pivot position in response to outflow from passage 73 of diverter element 7] thereby rolling up curtain 40 and permitting outflow from aperture 45. When outflow from diverter element 7] is through passage 75, leakage through hole 65 permits leaky bucket 71 to assume its uppermost pivot position (horizontal), causing the roller curtain to close and block outflow from aperture 45.

The above described roller curtain concept represents a departure from the pure fluidic (no moving parts) approach associated with the remaining aspects of the present invention; however, it can easily be understood that the mechanical details of the roller curtain control are fundamentally simple, reliable, and inexpensive and that fluidic control of the leaky bucket position is simply achieved. It should also be noted that both the roller curtain gate and the leaky bucket actuating approach can be utilized independent of one another and have individual utility when employed with conventional sensing, actuating, and/or flow modulating devices. For example, the roller curtain may employ actuators for rolling and unrolling curtain 40 sideways rather than up and down.

It should also be noted that, in order to conserve water, the water which leaks through the drain holes 65 in leaky bucket 41, and the water which is dumped from outlet passage 75 of diverter element 71 can be dumped directly into a main irrigation ditch such as a ditch fed by either outlet passage of diverter 49. The utilization of diverter element 49 at aperture 45 is optional depending upon system requirements as regards the outflow from aperture 45.

Referring now specifically to FIG. 6 of the accompanying drawings there is illustrated in schematic form an alternate method for controlling the actuation of a roller curtain water gate. in the arrangement illustrated in FIG. 6 the actuating mechanism is completely contained within the water container 43. As is the case with the embodiment illustrated in FIG. 3, the roller curtain 40 has one edge secured to the inside surface of the sidewall 47 and is positioned so as to be selectively rolled and unrolled over aperture 45. A bucket 8| is secured at its bottom to a fork link member 83 disposed within container 43 and pivoted at one end about a fixed pivot point 85. The opposite end of fork link member 83 contains two prongs, each of which engages a respective end of curtain roller 55. The arrangement is such that when fork link member 83 is horizontal the roller 55 is forced by member 83 to roll up and permit outflow from the container via aperture 45. When fork link member 83 pivots downwardly about pivot point 85 the roller 55 is forced to roll downwardly causing the roller curtain 40 to unroll and cover the aperture 45 in sealing relationship with wall 47.

The sidewall of bucket 81 extend above the maximum water level in container 43. Inflow of water into bucket 81 is controlled by means of a fluidic diverter element 87 mounted within bucket 81 and having its power nozzle inlet opening communicating with the water of container 43 via an aperture 89 defined through a wall of bucket 81. Water supplied to element 87 is selectively diverted to either of diverter outlet passages 89 and 91 by conventional control means such as aspiration control tubes 86, 88 communicating with respective control ports. When the water is diverted to outlet passage 91 it is dumped into bucket 81. When the water is diverted to outlet passage 89 it is conducted by a flexible tubing 90 through the walls of both the bucket 81 and container 43 to the irrigation ditch 92. A bucket drain opening 93 is defined through a wall of bucket 81 near its bottom and serves, via flexible tubing 94, to drain liquid from the bucket to ditch 92. A flotation collar 95 is secured to the exterior of bucket 81 to provide the necessary buoyancy for preventing downward pivoting of the fork link member 83 when bucket 81 is empty. When the bucket 81 is filled to a predetermined level, the weight of the water contents causes the fork link member 83 to pivot downwardly which causes curtain 40 to unroll over aperture 45 and shut oh the main water outflow to the diverter element 49.

As was the case with the embodiment illustrated in FIGS. 3 and 4, the inflow rate of bucket 81 via outlet passage 91 of diverter elements 87 is approximately twice the outflow rate from bucket 81 via drain opening 93. When it is desired to close the roller curtain gate, flow from diverter element 87 is directed to outlet passage 91 causing the bucket 81 to take on sufficient water to cause the fork link member 83 to pivot downwardly about pivot point 85. When it is desired to open the roller curtain gate the outlet flow from diverter element 87 is diverted to outlet passage 89 permitting the bucket 81 to empty via drain opening 93. The buoyancy provided by flotation collar 95 causes the bucket 81 and the fork link member 83 secured thereto to be restored in their horizontal position. It is to be noted once again that the drain water from both the pilot or control diverter element 87 and the bottom of bucket 81 is dumped into an irrigation ditch 92 being fed by outflow from aperture 45.

Referring now specifically to FIG. 7 of the accompanying drawings, there is illustrated in diagramatic form the roller curtain gate and control arrangement described in reference to FIGS. 3, 4, and 5 employed as a level control in an irrigation ditch. Specifically, the left control nozzle 77 of pilot diverter element 71 is in fluid communication with an inverted level sensing cup 101. Level sensing cup 101 is supported in an inverted position over an irrigation ditch 103 with the mouth of the cup positioned at a desired water reference level AA. The arrangement of FIG. 7 prevents the water level in ditch 103 from becoming higher than reference level A-A. A fluid passage or tubing 105 communicates between the interior of inverted cup 101 and left control nozzle 77. The right control nozzle 79 is provided with a bias restriction 107 to restrict aspirated air inflow to diverter element 71 via nozzle 79. In this manner, when the water level in irrigation ditch 103 is below reference level A-A, the rate of aspirated air inflow through cup 101 and into control nozzle 77 exceeds the rate of aspirated air inflow into control nozzle 79. The power stream in diverter element 71 therefore is directed through right outlet passage 73 and into the leaky bucket 41. The bucket begins to fill and eventually is caused to pivot downwardly whereby roller curtain 40 opens to permit outflow from container or reservoir 43 via aperture 45 into the irrigation ditch 103. When the water level in irrigation ditch 103 reaches reference level A-A, air inflow into inverted level sensing cup 101 is blocked by the water. Air inflow via right control nozzle 79 thus exceeds air inflow via left control nozzle 77 causing the power stream to switch to left outlet passage 75. The bucket 41 is thus permitted to empty via drain holes 65 and the weight of roller 55 and curtain 40 permit the later to unroll while the bucket 41 pivots upwardly. Aperture 45 is now blocked.

It is to be noted that outflow via aperture 45 from container 43 greatly exceeds the drain flow from outlet passage 75 of diverter element 71 and the leak flow through leakage holes 65 in leaky bucket 41. In fact the latter two flows are relatively insignificant as compared to the outflow from aperture 45 so that the leakage and drain flows produce no significant rise in the water level in irrigation ditch 103.

It should be pointed out that the arrangement of HG. 7 could readily be used to monitor the water level in container 43 rather than in irrigation ditch 103 By simply supporting the inverted sensor cup 101, with its mouth at the desired level, outflow via aperture 45 from tank 43 can be controlled to keep the container water level at or below that desired level. In this case blockage of aspiration through the sensor cup would initiate water flow to bucket 41 via diverter 71 and inflow from the sensor cup would prevent filling of the bucket.

Referring now specifically to FIG. 8 of the accompanying drawings, there is diagrammatically illustrated an alternate scheme for controlling the level in an irrigation ditch. It this embodiment water from container 43 issues from aperture 45 in wall 47 and is conducted to a supply inlet 111 of a fluidic vortex amplifier 113. Vortex amplifier 113 is a conventional, cylindrically configured element having an axially oriented outlet 115, a radially oriented supply flow inlet 111, and a tangentially oriented control flow inlet 117. A bistable fluidic pilot diverter 119 receives pressurized fluid, for example from container 43, and provides a power stream which is selectively diverted to either of outlet passages 121 and 123. Outlet passage 121 of pilot diverter 119 is connected to the tangential control flow inlet 117 of vortex amplifier 113; the flow from outlet passage 123 of diverter element 119 is dumped into irrigation ditch 125. Once again, the fluid flow through diverter 119 is significantly less than through aperture 45. Switching control for diverter 119 is accomplished in the same manner as switching control of diverter element 71 in FlG. 7. Specifically, left control nozzle 127 aspirates air through an inverted level sensor cup 129 having its mouth or rim sup ported at reference level AA. Right control nozzle 131 is restricted to a greater extent than is left control nozzle 127 so that diverter 119 is normally biased to provide outflow from outlet passage 123.

The operation of the vortex amplifier 113 is well known. If control flow is absent, the supply flow applied to supply inlet 111 proceeds directly through outlet in a radial direction through the cylindrical interior of amplifier 113. Outlet flow from outlet 115 is dumped into irrigation ditch 125. If control is introduced via inlet 117, the momentum exchange between the supply and control flows imparts a tangential component to the supply flow which then must reach the outlet 115 by a spiral or vertical rather than a radial path. This flow increases in tangential velocity by coriolis acceleration and also greatly increases in centripetal acceleration toward the center of the vortical path. The centripetal acceleration thus provides a considerable flow impedance to fluid approaching outlet 115, decreasing the outflow with increasing control flow. The change in outlet flow is essentially inversely proportional to the control flow. Vortex amplifiers can be designed to give maximum to minimum outflow ratios on the order of 10, thereby providing a very useful proportional flow control capability. Thus, when the water level in irrigation ditch achieves level AA', aspirated air inflow to control nozzle 127 of diverter element 119 is blocked causing the power stream diverter element to switch to outlet passage 127 and control inlet 117 of vortex amplifier 113. The resulting regulatory action of the supply flow in the vortex amplifier proceeds as described above. It will be appreciated that diverter element II9 may operate in either a bistable or proportional mode.

As will be described subsequently in relation to FIG. I2, one aspect of the present invention contemplates level sensing with a slotted inverted sensor cup whereby aspirated air inflow to a diverter control port is rendered proportional to the sensed liquid level rather than merely being present or absent, at any given instant of time. If such a proportional level sensor is employed, the diverter element I19 may be a proportional type fluidic amplifier, for example diverter I01 of FIG. 2, which inturn acts to proportionally throttle the flow between reservoir or container 43 and irrigation ditch I25 via vortex amplifier II3.

Referring now specifically to FIG. 9 of the accompanying drawings there is illustrated diagrammatically a fluidically controlled siphon arrangement by means of which water or liquid in a container or reservoir 135 can be selectively made to flow to a desired location, for example to an irrigation ditch. Siphon I37 comprises a tube having its open upstream end in fluid communication with water in reservoir I35, either through an appropriate opening in a wall of the reservoir as illustrated, or by extending over the top of the reservoir wall. The siphon tube has an inverted generally U-shaped configuration with a short horizontal section at its upstream end. The apex or gooseneck section of the siphon tube extends to a height which is above the maximum water level in reservoir I35. The downstream end of the siphon tube extends into a catch basin I39 having a main discharge of tlume M] which permits egress of water from the catch basin whenever the water level exceeds the level at the mouth of the flume. The downstream end of the siphon tube extends into catch basin I39 below the level of the mouth of flume 14I.

A bistable fluidic pilot diverter valve I43 receives water under pressure from reservoir I35 at its power nozzle I45 via an appropriate opening or aperture in the sidewall of the reservoir. Diverter valve I43 has respective left and right control ports I47 and I49 of the aspiration type and left and right output passages 151 and I53 respectively. Outlet passage I53 is arranged to discharge water received thereby directly into catch basin I39. Outlet passage I51 is provided with a venturi section I55 at its downstream end which is also arranged so that water received by outlet passage I is discharged into the catch basin 139. The neck of venturi section I55 is in fluid communication with the interior of siphon I37 at the apex or gooseneck of the latter by means of a suction tube I57.

In operation, when right control port I49 is blocked and left control port 147 is open to permit aspiration of air to element I43, the water power stream discharges from right outlet passage I53 into the catch basin 139. Water in the catch basin eventually covers the downstream end of the siphon. The catch basin continues to fill until the water overflows the discharge flume MI. The water level in the siphon on the upstream side of the siphon gooseneck adjusts to water level in reservoir I35.

When the left control port I47 is blocked and aspiration of air is permitted only through right control port 149 the power stream flow in diverter element I43 issues from left outlet passage I5I into catch basin I39 via venturi section I55. Power stream flow through the venturi section causes a suction or negative pressure in suction tube 157 which draws air from the top of the gooseneck section of the siphon, raising the water level therein in both the upstream and downstream sections. When the level in the upstream section of the siphon I37 rises over the gooseneck section, flow between the reservoir I35 and catch basin begins. With continued aspiration by means of venturi section I55 the siphon achieves full flow.

If now left control port I47 is opened and the right control port 149 is blocked the fluidic element again switches away from venturi section I55 to outlet passage I53. Ambient air now flows into the downstream end of venturi section 155 and through suction tube 157 to the siphon gooseneck, increasing the pressure thereat and terminating siphon flow.

It is noted that both outlet passages ISI and 153 of pilot diverter I43 are arranged to discharge fluid into catch basin 139. This is required to maintain the downstream end of the siphon I37 under water so that air can be drawn out of the siphon gooseneck when desired. It is also important that the venturi section of outlet passage I51 be at least partially elevated from the quiescent water level in the fluidic diverter element I43 so that air can enter suction tube I57 and flow to the siphon gooseneck when the diverter element switches to outlet passage I53. It is this air which, upon entering the downstream end of venturi section I55, increases the interior pressure in the siphon sufficiently to stop siphon flow. A further consideration to bear in mind is that the pilot diverter element I43 runs continuously so that its output flow should be kept a minimum.

I have found that the negative pressure or suction which can be generated in the venturi section I55 is approximately fifty to sixty percent of the positive pressure head available at the power nozzle I45. This of course provides a limit as to the height to which water can be raised in the siphon by the suction action of the venturi section.

The fluidically controlled siphon can be modified for proportional flow control as well as on-off control. For example. if fluidic element I43 is of the analog or proportional type, the negative pressure generated in the venturi section I55 varies proportionally with flow therethrough. Consequently the height to which water can be drawn over the siphon gooseneck is proportional to power stream flow in outlet passage 15!. In such an arrangement, the water velocity through the gooseneck section of the siphon 137 should be kept sufficiently low in order that water flow does not entrain air in the top of the gooseneck. The latter condition would cause the siphon to run at full flow rather than as a controlled proportional function of flow diversion in element I43.

Referring now to FIG. 10 of the accompanying drawings there is illustrated a modification of the arrangement of FIG. 9 whereby the siphon gooseneck or arch is capable of being swiveled to provide an adjustable gooseneck height. The only substantial difference in the arrangements between FIG. 9 and FIG. I0 therefore resides in the provision of two rigidly supported fluid fitting members I6I and I63 which are adapted to receive, in fluid-tight relation, the respective upstream and downstream ends of the gooseneck section of siphon tube I37. The gooseneck section is rotatable in both of the fluid fitting members 161 and I63 so that the height of the gooseneck may be selectively adjusted. The suction tube I57 connecting the siphon arch and the venturi section I55 is of course made flexible in order to accommodate the various possible positions of the movable siphon arch. Upstream fitting member I6! provides fluid communication between the gooseneck section and reservoir I35 via the upstream section of the siphon. The downstream fitting member 163 provides fluid communication between the gooseneck and the catch basin 139 via the downstream section of the siphon.

In operation, the arrangement of FIG. I0 performs identically to the arrangement of FIG. 9 except that the arrange ment of FIG. 10 is able to perform in response to lower flow rates through venturi section I55 of elements I43. More specifically, by lowering the siphon arch sufficiently, the water in the siphon can be raised to permit the siphon flow even when the pressure head applied to the diverter element is relatively low.

Referring now to specifically to FIG. II of the accompanying drawings there is illustrated in diagrammatic form an alternate arrangement for fluidically controlling siphon flow. In order to eliminate the venturi section I55 in FIGs. 9 and I0, diverter element 143 is replaced by diverter element I65 which is ofthe type described above in relation to FIG. I. As is the case with the arrangement of FIG. 9, the siphon tube I37 has its upstream end communicating with the liquid contents of reservoir I35 and its downstream end disposed in catch basin I39. Diverter element I65 has its inlet opening communicating with the liquid in reservoir I35 and the pressurized liquid is selectively discharged through either of outlet passages 167 or 169 into catch basin 139. A standpipe I71, comprising a hollow tube, is located with its open bottom end near the exit of outlet passage 169. More specifically the bottom end of standpipe 171 is disposed slightly above the top of the downstream weir 173 in passage 169. Standpipe 171 communicates directly with suction tube 157 which, as described in relation with FIG. 9, communicates with the top of the gooseneck of siphon tube 137. In addition, left control port 175 of diverter 165 communicates via fluid passage 177 with a junction between the stand pipe 171 and suction tube 157.

It is important that the bottom of the standpipe 169 be disposed slightly above the weir I73 so that when diverter flow issues from outlet passage 167 air can enter the standpipe and flow to the siphon gooseneck to stop siphon flow. If the standpipe extended below the weir 173 the residual water level of the diverter element 165 would block the bottom of the standpipe, even without flow through passage 169, and thereby block the required air flow. When diverter flow issues from passage 169 the water covers the bottom of the standpipe preventing any substantial air flow into suction tube 157 from standpipe 17].

The operation of the arrangement in FIG. 11 is as follows: When right control port 179 of diverter element 165 is initially uncovered, there is no siphon flow. Water entering the diverter element 165 initially tends to divide between the outlet passages 167 and 169 because of relatively equal air flows entrained into both control ports 179 and 175. As air is drawn from the siphon arch into left control port 175 via passage I77 and suction tube 157 and into standpipe 171 via suction tube I57, the flow in diverter element 165 gradually switches to left output passage 169. More particularly, the inflow to control port 179 remains substantially the same whereas the inflow to control port 175 gradually decreases as more and more of the limited air supply is sucked out of the siphon gooseneck. As more flow switches to left outlet passage 169 the suction capability of control port 175 increases due to the increasing vortical flow in the vortex projection associated with control port 175. The increasing suction raises a column of water in standpipe 171, When enough air is drawn from the siphon 137 water flows over the gooseneck and siphon flow begins. As the flow in the siphon increases, the remaining air in the siphon is washed out by the water flow and the siphon achieves the full flow mode.

When right control port 179 of diverter 165 is blocked, air flow thereinto stops and the power stream begins to switch toward outlet passage 167. When the switching is nearly completed, the water level in outlet passage I69 drops below the bottom of standpipe 171 permitting air to enter the standpipe and be entrained by siphon flow into the siphon via suction tube 157. Air entering standpipe 171 is also entrained into control port 175 assuring that the diverter flow remains directed toward outlet passage 167. The air entering the siphon gradually increases the pressure therein and terminates siphon flow.

As mentioned above, the siphon arrangement illustrated in FIGS. 9, I and 11 need not communicate through a all of the reservoir but instead may be disposed so that the siphon gooseneck straddles the reservoir wall. There is no substantial change in the operation of such an arrangement as compared with the arrangements illustrated in FIGS. 9 through 11.

Referring now specifically FIG. 12 of the accompanying drawings there is illustrated a proportional type fluidic liquid level control arrangement. A lluidic analog diverter 180 of the type illustrated in FIG. 2 distributes its outlet flow between left and right outlet passages 18I and 183 as a proportional function of the liquid level in a container 185. In the particular arrangement chosen for illustration in FIG. 12, outlet flow from right outlet passage 183 is issued into container 185 and outlet flow from left outlet passage 181 is issued into a bypass flow channel 187. By virtue of this arrangement, the liquid in the container is maintained at a desired level even as liquid is withdrawn from the container. A left control port 189 communicates by means of tubing 191 with an inverted level sensing cup 193. The mouth of cup I93 extends downwardly into container 185 to some desired depth. The cylindrical sidewall of up 193 has multiple slots defined through most of its length. Right control port 195 of diverter element serves as a bias port and in this regard is somewhat smaller in cross section than control port 189.

When tank is empty, air is aspirated via the mouth and slots of sensor cup 193, through tubing I91, into left control port 189. Since the ambient air inflow to left control port 189 is larger than to the smaller right control port I95, substantially more of the power stream water flows through right out put passage 183 than through left output passage 18]. As the water level in container 185 rises, the aspirated air flow into left control port 189 decreases because the rising water level gradually decreases the area through which air can pass into sensor cup 193. Decreased inflow of air into control port 189 causes the power stream to deflect more towards left output passage 181. By properly correlating the cross sectional openings of control ports I89 and 195, the power stream flow in element 180 can be designed to issue entirely from left output passage 181 when the liquid in container 185 achieves a predetermined level. Thus, as the liquid is utilized or otherwise withdrawn from container 185, the flow in element 180 is correspondingly proportioned between output passages 181 and 183 to maintain the desired container water level.

The proportional or analog liquid level control concept embodied in FIG. I2 is readily adaptable to the level control arrangements described above in relation to FIGS. 7 and 8 by simply employing slotted sensor cups and proportional diverter element.

In addition to slotting the sidewall of the sensor cup, proportional or analog sensing of liquid level may be achieved by providing a sensor cup with one or more vertical rows of small holes. In this case as well as the slotted configuration, a rising level gradually decreases the area through which the aspirated air can enter the cup.

Referring now to FIG. 13 of the accompanying drawings there is diagrammatically illustrated an arrangement for sensing the water level in an irrigation ditch 203. The sensor comprises a shallow basin 20I placed in the ditch and having inlet leakage holes 205 defined through its sidewall near the bottom of the basin. An inverted level sensor cup 207 is disposed with its mouth supported at a predetermined level in basin 201. The cup has a sufficiently large diameter to prevent capilliary action from keeping water in the cup when the water level in the basin drops below the cup mouth or rim. The closed end opposite the mouth of the inverted cup 207 communicates via tube 209 with the control port of a fluidic diverter element such as is employed in FIG. I and which controls flow to one or more irrigation ditches, including ditch 203. When the water level in basin 20] reaches the mouth of cup 207, the water level in cup 207 is raised by the aspiration action associated with the control port of the diverter element.

When water rises in cup 207 the supply of aspirated air to the diverter element via tube 209 is terminated causing the diverter element to switch and terminate the supply of water to irrigation ditch 203. The purpose of the shallow basin 201 is to minimize currents in the vicinity of the rim of the cup 207 so as to improve the sensitivity of the cup and prevent cut-off of aspirated air by waves occurring in the ditch 203. It is apparent that by adjusting the height of the cup rim it is possible to vary the maximum depth to which irrigation ditch 203 is to be filled.

It is important that the height of the cup be sufficient to provide an air dome above the air level in the sensing cup. The water level is thus permitted to rise a few inches inside the cup but does not enter the air line 209 to the control port of the diverter element. Water in line 209 would tend to clog the line and prevent reliable switching action at the diverter element.

In a practical application of the arrangement in FIG. I3, basin 201 is placed at or proximate the downstream end of ditch 203 to assure that the water has achieved the desired level throughout the entire length of the ditch. When the ditch 

1. A fluidic diverter element adapted for use in a specified ambient fluid environment to selectively distribute a working fluid between at least two flow paths, said working fluid having a greater density than said ambient fluid, said element comprising: an interaction region; a power nozzle having an inlet opening and responsive to application of pressurized working fluid to said inlet opening for issuing a power stream of said working fluid into said interaction region; at least one outlet passage having an ingress opening disposed for receiving said power stream at the downstream end of said interaction region, said outlet passage having an open downstream end; weir means for preventing outflow of said working fluid from the open downstream eNd of said outlet passage unless the fluid pressure at the ingress opening of said outlet passage exceeds a predetermined minimum pressure; and control means for selectively deflecting said power stream relative to said outlet passage such that for at least one position of said power stream the fluid pressure at the ingress opening of said at least one outlet passage exceeds said predetermined minimum pressure.
 2. The fluidic diverter element according to claim 1 wherein said working fluid is a liquid, wherein said interaction region has at least one sidewall and wherein said control means comprises: a vortex chamber projecting outwardly from said interaction region through an upstream section of said sidewall, said vortex chamber being disposed to receive a small portion of said power stream and create vortical flow thereof in said vortex chamber, and a control port communicating between ambient pressure and said vortex chamber axially of said vortical flow, whereby said vortical flow creates a suction at said control port to induce inflow of ambient fluid into said interaction region.
 3. A system employing a liquid working fluid and the fluidic diverter element of claim 2 for maintaining the liquid level in one of said two flow paths at a predetermined level, said system further comprising a sensor cup, means for supporting said sensor cup with its open end facing downward and the rim of said open end disposed at said predetermined level in said one of said flow paths, and a fluid passage interconnecting the interior of said cup and said control port such that ambient fluid is supplied from said sensor cup to said control port unless the open end of said sensor cup is blocked by the liquid in said one of said flow paths.
 4. A system employing the fluidic diverter element of claim 2 and a liquid as a working fluid, said system further comprising: a metering cup, open at its top, and having an adjustable drain orifice at its bottom; means for conducting a known small proportion of said liquid flowing through said one outlet passage into said metering cup; a sensor tube having one end extending a predetermined depth into said metering cup and a second end connected to said control port of said diverter element; whereby upon the liquid in said metering cup rising to the level of said one end of said sensor tube, inflow of ambient fluid to said control port is terminated and liquid flow through said one outlet passage ceases.
 5. The fluidic diverter element according to claim 2 wherein said one sidewall is positioned to permit boundary layer lockon thereto by said power stream, and wherein said power stream is directed toward said one outlet passage when said power stream is locked onto said one sidewall, said predetermined minimum pressure at said one outlet passage being exceeded when said power stream is locked onto said one sidewall.
 6. The fluidic diverter element according to claim 5 wherein the size of said control port permits sufficient ambient fluid inflow to said interaction region to provide deflection of said power stream relative to said one outlet passage as a proportional function of the ambient fluid inflow rate.
 7. The fluidic diverter element according to claim 5 wherein said diverter element comprises top and bottom joined plates, said weir means being formed by a surface in said bottom plate which slopes upwardly toward said top plate in a downstream direction at the downstream end of said outlet passage.
 8. The fluidic diverter element according to claim 1 further comprising: a second outlet passage having an ingress opening disposed for receiving said power stream at the downstream end of said interaction region, said one and said second outlet passages being separated by a flow splitter, said second outlet passage having an open downstream end; further weir means for preventing outflow of said working fluid from the open downstream end of second outlet passage unless the fluid pressure at the ingress opening of said second outlet passage exceeds a specified minimum pressure; and first and second sidewalls for said interaction region, said sidewalls being positioned such that said power stream can lock onto either sidewall, and wherein said power stream is directed toward said one outlet passage and exceeds said predetermined minimum pressure thereat when locked onto said first sidewall and is directed toward said second outlet passage and exceeds said predetermined minimum pressure thereat when locked onto said second sidewall; and wherein said control means comprises first and second vortex chambers projecting outwardly from said interaction region through said first and second sidewalls respectively, each of said vortex chambers being disposed to receive respective small portions of power stream fluid tangentially of the vortex chamber to create vortical flow therein, each vortex chamber having a respective one of first and second control ports communicating between ambient fluid and said vortex chamber axially of said vortical flow, whereby said vortical flow creates a suction at said control port to induce inflow of ambient fluid into said interaction region
 9. The fluidic diverter element according to claim 8 wherein said diverter element is constructed from top and bottom joined plates, said weir means and said further weir means being formed by respective surfaces in said bottom plate which slope upwardly toward said top plate in a downstream direction at the downstream end of each of said outlet passages.
 10. A system employing the fluidic diverter element according to claim 8 wherein the working fluid is a liquid, said system being employed for maintaining the liquid level in one of said two flow paths at a predetermined level, said system additionally comprising: a sensor cup, means for supporting said sensor cup with its open end facing downward and the rim of said open end disposed at said predetermined level in said one of said two flow paths; and a fluid passage interconnecting the interior of said cup with the one of said control ports communicating with said first vortex chamber such that ambient fluid is supplied from said sensor cup to said one control port unless the open end of said sensor cup is blocked by the liquid level in said one flow path.
 11. An irrigation system employing the combination according to claim 10 wherein said ambient fluid is ambient air and further comprising override means operative in conjunction with said control means for limiting inflow of ambient air to said one of said control ports whenever an ambient environment parameter has a value lying outside a predetermined range of values, said override means including: a flow tube having one end in fluid communication with said fluid passage and an open second end; and sensing means for selectively blocking and unblocking said second end of said flow tube in accordance with whether or not said ambient environment parameter has a value within said predetermined range of values; wherein the relative sizes of said control ports are such that said power stream attaches to said first sidewall only when the rim of said sensor cup is not blocked by liquid in said one flow path and the second end of said flow tube is not blocked by said sensing means.
 12. The system according to claim 11 wherein said ambient environment parameter is ambient temperature.
 13. The system according to claim 11 wherein said ambient environment parameter is ambient temperature and wherein said sensing means comprises: a bi-metal strip fixedly secured at one end and responsive to temperature increases above a predetermined nominal temperature for pivoting about said one end in a first direction and responsive to temperature decreases below said predetermined nominal temperature for pivoting about said one end in a second and opposite direction; and means secured to said bi-metal strip for blocking said second end of said sEnsor tube whenever said bi-metal strip pivots a predetermined angle in one of said first and second directions.
 14. The system according to claim 11 wherein said ambient environment parameter is wind velocity, and wherein said sensing means comprises a movably mounted tube having one end in flow communication with the second end of said sensor tube and its other end open to ambient air, a plurality of vane members secured to said movably mounted tube proximate said other end such that wind forces acting on said vane members tend to move said movably mounted tube to a position in which said other end faces downstream of the wind and air is aspirated therefrom by the wind, whereby for wind velocities below a specified level sufficient air inflow is provided to said other end of said movably mounted tube to cause said power stream to attach to said first sidewall if the level of liquid in said one flow path is below said predetermined level.
 15. The fluidic diverter element according to claim 8 wherein the sizes of said control ports permit sufficiently large inflow rates of ambient fluid into said interaction region to provide deflection of said power stream relative to said outlet passages as a proportional function of the ambient fluid inflow rate.
 16. The system according to claim 15 wherein said working fluid is a liquid and said ambient fluid is air and wherein said system is employed to balance liquid inflow between two liquid containers in accordance with the difference between outflows from said two containers, said system further comprising: first variable flow restriction means disposed in a first of said two liquid containers and connected in flow communication with said first control port for restricting the flow of ambient air to said first control port as a proportional function of the liquid level in said first container; and second variable flow restriction means disposed in the second of said two containers and connected in flow communication with said second control port for restricting the flow of ambient air to said second control port as a proportional function of the liquid level in said second container; and means for directing liquid flowing through said first outlet passage into said first container and liquid flowing through said second outlet passage into said second container; whereby the difference between liquid levels in said two containers determines the difference between liquid inflows to said two containers.
 17. The system according to claim 16 wherein said variable flow restriction means each comprise a cup having an open end disposed proximate the bottom of a respective container, a closed end extending upwardly to some higher level in the container, a fluid passage communicating between the closed end of said cup and a respective control port, and a plurality of openings in the side of the cup arranged so that increasingly greater portions of the total area of said openings are blocked by a rising liquid level in said container.
 18. The system according to claim 16 further comprising a bistable fluidic diverter element having two outlet passages, one of which is connected directly to the power nozzle the proportional fluidic diverter element, and means for selectively switching pressurized liquid from one to the other of the outlet passages of said bistable fluidic diverter element.
 19. The system according to claim 16 further comprising a second substantially identical proportional diverter element for distributing liquid inflow between two further liquid containers in accordance with the difference between liquid levels in said two further containers as sensed by two further variable flow restriction means, said system further comprising a bistable fluidic element having first and second outlet passages and means for selectively switching a liquid power stream from one to the other of said last-mentioned outlet passages, and means for connecting said last-mentioned outlet passages to the poweR nozzles of respective ones of said proportional diverter elements.
 20. A fluidic diverter element comprising an interaction region, a power nozzle responsive to application of pressurized fluid thereto for issuing a power stream of fluid into said interaction region, at least one outlet passage disposed in receiving relation to said power stream at the downstream end of said interaction region, at least one sidewall of said interaction region disposed to permit boundary layer lockon thereto by said power stream, at least one control port defined through said sidewall and communicating between ambient fluid and said interaction region, said one control port being disposed such that ambient fluid is entrained therethrough by said power stream, wherein the size of said control port permits sufficient ambient inflow to said interaction region to deflect said power stream as a proportional function of the ambient fluid inflow rate and further including a vortex chamber projecting outwardly from said interaction region through said sidewall and disposed to receive a small portion of said power stream tangentially of said vortex chamber to create vortical flow in said vortex chamber, and wherein said control port communicates between an ambient fluid environment and said vortex chamber axially of said vortical flow, whereby said vortical flow creates a suction for inducing inflow of ambient fluid into said interaction region.
 21. A fluidic diverter element comprising an interaction region, a power nozzle responsive to application of pressurized fluid thereto for issuing a power stream of fluid into said interaction region, at least one outlet passage disposed in receiving relation to said power stream at the downstream end of said interaction region, at least one sidewall of said interaction region disposed to permit boundary layer lockon thereto by said power stream, at least one control port defined through said sidewall and communicating between ambient fluid and said interaction region, said one control port being disposed such that ambient fluid is entrained therethrough by said power stream, wherein the size of said control port permits sufficient ambient inflow to said interaction region to deflect said power stream as a proportional function of the ambient fluid inflow rate, and wherein said diverter is employed to monitor liquid level in a container and further comprises: a sensor cup having an open end, a closed end, at least one sidewall and a vertically extending slot defined through said sidewall, said sensor cup being disposed in said container with said open end facing downward; and a tube for providing fluid interconnection between the interior of said sensor cup at the closed end thereof and said at least one control port of said fluidic diverter element; whereby inflow of ambient fluid to said at least one control port via said vertically extending slot is restricted as a function of the level of liquid in said container.
 22. A fluidic diverter element capable of operating in either a proportional mode or bistable mode, said diverter element comprising: an interaction region; a power nozzle responsive to application of pressurized fluid thereto for issuing a power stream of fluid into said interaction region; first and second outlet passages disposed for receiving respective portions of said power stream at the downstream end of said interaction region as a function of deflection of said power stream; first and second control ports communicating between an ambient fluid environment exterior of said diverter element and said interaction region at respective opposite sides of said power stream and adapted to permit aspiration of ambient fluid by said power stream into said interaction region; a pair of sidewalls defining opposite sides of said interaction region and disposed such that when air inflow from said control ports is at less than a predetermined flow rate said power stream is stable only when attached to either of said Sidewalls; wherein said control ports are sufficiently large to prevent attachment of said power stream to said sidewalls unless said control ports are completely blocked to ambient fluid flow; and further comprising: first and second insert means adapted to fit over said first and second control ports respectively for restricting ambient fluid inflow through said control ports sufficiently to render said power stream stable only when attached to either of said sidewalls; and first and second projections extending outwardly from respective sidewalls of said interaction region immediately downstream of said power nozzle and configured to scoop off respective portions of said power stream to create vortical fluid flow therefrom in said projections, wherein said first and second control ports communicate with said interaction region through respective ones of said first and second projections in axial relation to the vortical flow in said projections.
 23. A fluidic diverter element capable of operating in either a proportional mode or bistable mode, said diverter element comprising: an interaction region; a power nozzle responsive to application of pressurized fluid thereto for issuing a power stream of fluid into said interaction region; first and second outlet passages disposed for receiving respective portions of said power stream at the downstream end of said interaction region as a function of deflection of said power stream; first and second control parts communicating between an ambient fluid environment exterior of said diverter element and said interaction region at respective opposite sides of said power stream and adapted to permit aspiration of ambient fluid by said power stream into said interaction region; a pair of sidewalls defining opposite sides of said interaction region and disposed such that when air inflow from said control ports is at less than a predetermined flow rate said power stream is stable only when attached to either of said sidewalls; wherein said control ports are sufficiently large to prevent attachment of said power stream to said sidewalls unless said control ports are completely blocked to ambient fluid flow; and a system employing said fluidic diverter element and utilizing a liquid as a working fluid, said system comprising: a metering cup, open at its top, and having an adjustable drain orifice at its bottom; means for conducting a known small proportion of liquid flowing through said one of said outlet passages into said metering cup; sensor tube having one end extending a predetermined depth into said metering cup and a second end connected to one of said control ports of said diverter element; whereby upon the liquid in said metering cup rising to the level of said one end of said sensor tube, inflow of ambient fluid to said one of said control ports is terminated and liquid flow through said one of said outlet passages ceases.
 24. A fluidic diverter element capable of operating in either a proportional mode or bistable mode, said diverter element comprising: an interaction region; a power nozzle responsive to application of pressurized fluid thereto for issuing a power stream of fluid into said interaction region; first and second outlet passages disposed for receiving respective portions of said power stream at the downstream end of said interaction region as a function of deflection of said power stream; first and second control ports communicating between an ambient fluid environment exterior of said diverter element and said interaction region at respective opposite sides of said power stream and adapted to permit aspiration of ambient fluid by said power stream into said interaction region; a pair of sidewalls defining opposite sides of said interaction region and disposed such that when air inflow from said control ports is at less than a predetermined flow rate said power stream is stable only when attached to either of said sidewalls; wherein said control ports are sufficiently large to prevent attachment of said power stream to said sidewalls unless said control ports are completely blocked to ambient fluid flow; and a system employing a liquid working fluid and said fluidic diverter element for maintaining the liquid level in a flow path at a predetermined level, said system comprising: means conducting liquid from one of said outlet passages to said flow path; a sensor cup; means for supporting said sensor cup with its open end facing downward and the rim of said open end disposed at said predetermined level in said flow path; and a fluid passage interconnecting the interior of said cup and one of said control ports such that ambient fluid is supplied from said sensor cup to one of said control ports unless the open end of said sensor cup is blocked by the liquid in said flow path.
 25. An irrigation system employing the combination according to claim 24 wherein said ambient fluid is ambient air and further comprising override means operative for limiting inflow of ambient air to said one of said control ports whenever an ambient environment parameter has a value lying outside a predetermined range of values, said override means including: a flow tube having one end in fluid communication with said fluid passage and an open second end; and sensing means for selectively blocking and unblocking said second end of said flow tube in accordance with whether or not said ambient environment parameter has a value within said predetermined range of values; wherein the relative sizes of said control ports are such that said power stream attaches to said first sidewall only when the rim of said sensor cup is not blocked by liquid in said one flow path and the second end of said flow tube is not blocked by said sensing means.
 26. The system according to claim 25 wherein said ambient environment parameter is soil moisture content and wherein said sensing means comprises: a container at least partially buried in the soil having a funnel-shaped ingress opening at its top which extends above the soil for receiving rainfall, a drain passage at its bottom communicating between the container interior and the soil, and a sensor opening; porous material disposed in said container and having water-absorbing characteristics approximating those of the surrounding soil, said porous material surrounding said sensor opening so that ambient air flow from said ingress opening to said sensor opening must pass through said porous material; and means for preventing said porous material from lodging in said sensor opening; wherein the density of said porous material in said container is such that when said porous material is saturated with water, substantially no air flow can occur between said ingress and sensor openings, and when the amount of water absorbed by said porous material is at or less than some specified amount there is sufficient air flow from said ingress opening to said sensor opening to cause said power stream to attach to said first sidewall if the liquid level in said one flow path is below said predetermined level.
 27. The system according to claim 26 wherein said ambient environment parameter is ambient temperature.
 28. The system according to claim 26 wherein said ambient environment parameter is ambient temperature and wherein said sensing means comprises: a bi-metal strip fixedly secured at one end and responsive to temperature increases above a predetermined nominal temperature for pivoting about said one end in a first direction and responsive to temperature decreases below said predetermined nominal temperature for pivoting about said one end in a second and opposite direction; and means secured to said bi-metal strip for blocking said second end of said sensor tube whenever said bi-metal strip pivots a predetermined angle in one of said first and second directions.
 29. The system according to claim 26 wherein said ambient environment parameter is wind velocity, and whereiN said sensing means comprises a movably mounted tube having one end in flow communication with the second end of said sensor tube and its other end open to ambient air, a plurality of vane members secured to said movably mounted tube proximate said other end such that wind forces acting on said vane members tend to move said movably mounted tube to a position in which said other end faces downstream of the wind and air is aspirated therefrom by the wind, whereby for wind velocities below a specified level sufficient air inflow is provided to said other end of said movably mounted tube to cause said power stream to attach to said first sidewall if the level of liquid in said one flow path is below said predetermined level.
 30. A fluidic diverter element capable of operating in either a proportional mode or bistable mode, said diverter element comprising: an interaction region; a power nozzle responsive to application of pressurized fluid thereto for issuing a power stream of fluid into said interaction region; first and second outlet passages disposed for receiving respective portions of said power stream at the downstream end of said interaction region as a function of deflection of said power stream; first and second control ports communicating between an ambient fluid environment exterior of said diverter element and said interaction region at respective opposite sides of said power stream and adapted to permit aspiration of ambient fluid by said power stream into said interaction region; a pair of sidewalls defining opposite sides of said interaction region and disposed such that when air inflow from said control parts is at less than a predetermined flow rate said power stream is stable only when attached to either of said sidewalls; wherein said control ports are sufficiently large to prevent attachment of said power stream to said sidewalls unless said control ports are completely blocked to ambient fluid flow; and wherein said fluid is a liquid and said ambient fluid is air and wherein said diverter element is employed to balance liquid inflow between two liquid containers in accordance with the difference between outflows from said two containers, said system further comprising: first variable flow restriction means disposed in a first of said two liquid containers and connected in flow communication with said first control port for restricting the flow of ambient air to said first control port as a proportional function of the liquid level in said first container; and second variable flow restriction means disposed in the second of said two containers and connected in flow communication with said second control port for restricting the flow of ambient air to said second control port as a proportional function of the liquid level in said second container; and means for directing liquid flowing through said first outlet passage into said first container and liquid flowing through said second outlet passage into said second container; whereby the difference between liquid levels in said two containers determines the difference between liquid inflows to said two containers; a second substantially identical proportional diverter element for distributing liquid inflow between two further liquid containers in accordance with the difference between liquid levels in said two further containers as sensed by two further variable flow restriction means; a bistable fluidic element having first and second outlet passages and means for selectively switching a liquid power stream from one to the other of said last-mentioned outlet passages; and means for connecting said last-mentioned outlet passages to the power nozzles of respective ones of said proportional diverter elements.
 31. A fluidic diverter element capable of operating in either a proportional mode or bistable mode, said diverter element comprising: an interaction region; a power nozzle responsive to application of pressurized fluid thereto for issuing a pOwer stream of fluid into said interaction region; first and second outlet passages disposed for receiving respective portions of said power stream at the downstream end of said interaction region as a function of deflection of said power stream; first and second control ports communicating between an ambient fluid environment exterior of said diverter element and said interaction region at respective opposite sides of said power stream and adapted to permit aspiration of ambient fluid by said power stream into said interaction region; a pair of sidewalls defining opposite sides of said interaction region and disposed such that when air inflow from said control ports is at less than a predetermined flow rate said power stream is stable only when attached to either of said sidewalls; wherein said control ports are sufficiently large to prevent attachment of said power stream to said sidewalls unless said control ports are completely blocked to ambient fluid flow; and a system employing said fluidic diverter element in a bistable operating mode wherein said working fluid is a liquid, said second outlet passage being arranged to issue liquid flowing therethrough into a flow channel, said system further comprising sensing means located proximate the upstream end of said flow channel for simulating liquid level sensing at the downstream end of said flow channel and terminating liquid flow through said second outlet passage whenever the liquid level sensed by said sensing means reaches a predetermined level.
 32. The system according to claim 31 wherein said sensing means comprises: a standpipe located in said flow channel proximate said upstream end so as not to prevent downstream flow through said channel, said standpipe having an aperture extending therethrough at a level below said predetermined level to permit leakage of liquid from said channel into said standpipe; a sensor cup having an open end and a closed end and supported in said standpipe with said open end extending downward at said predetermined level; and fluid passage means communicating between the closed end of said sensor cup and the second control port of said diverter element; wherein the size of said aperture is chosen such that the rate of liquid level rise at the downstream end of said channel is simulated by the liquid level rise in said standpipe.
 33. The system according to claim 31 wherein said sensing means comprises: a sensor cup having an open end and a closed end and supported proximate the upstream end of said channel with said open end facing down at a specified level; a fluid passage line communicating between said closed end and said second control port; and an enclosure of predetermined volume communicating with said fluid passage line; whereby ambient air is aspirated from said enclosure after the liquid level proximate the upstream end of said channel reaches said specified level to cover the open end of said sensor cup, the volume of said enclosure being selected such that said enclosure is substantially evacuated at a time corresponding to that when the liquid at the downstream end of said channel reaches said predetermined level. 